The present disclosure relates to a technique for, in an image scanner and an image forming apparatus equipped with the image scanner, detecting that dew condensation occurs on a transparent member for placing a document thereon.
Heretofore, an image scanner has been configured to irradiate a document placed on a plate-shaped transparent member, with light from a light source, such as a fluorescent lamp or an LED, through the transparent member, and photoelectrically convert reflected light from the document by a photoelectric conversion element, thereby generating document image data as a scanned image of the document.
As one example of conventional art for determining that dew condensation occurs, there has been disclosed a technique of pre-storing, in a line memory, a data pattern obtained by scanning a reflector plate by one scanning line when no dew condensation occurs, and comparing data obtained by scanning the reflector plate by one scanning line at a timing of the determination, with the data pattern pre-stored in the line memory, wherein whether or not dew condensation occurs is determined based on whether or not they are coincident with each other.
However, in order to determine that dew condensation occurs, the conventional technique is required to ensure a storage area enough to pre-store therein data obtained by scanning an image of a dew-condensation determination member (reflector plate) by one line in a main scanning direction (by one scanning line) in the form of a plurality of pixels, in a situation where no dew condensation occurs.
In view of the above circumstance, it is an object of the present disclosure to provide an image scanner and an image forming apparatus capable of reducing an amount of data to be pre-stored for determining that dew condensation occurs on a transparent member for placing a document thereon.